For the topping, combine butter, 1 ½ cups flour, brown sugar and rolled oats together. It's best to mix it with your hands.
Sprinkle over fruit mixture.
Bake 35-40 minutes, edges will bubble.
Serve with vanilla ice cream or whipped cream if desired.
Don't waste your time peeling peaches! It is NOT necessary. No one will notice, they blend right in.
You have some flexibility with the white sugar. I like ¼-1/2 cup if I'm using fresh, in-season, fruit. Or, if I obtained that fruit during its peak season and then froze it. If not, I might use up to ¾ cup sugar to help sweeten it up. All depends on YOUR taste.
You can use frozen fruit instead of fresh. Don't thaw it. Give it a few extra minutes of bake time.
A stand mixer is a great shortcut for combining the topping, but you can use a pastry blender or just your hands. I use a stand mixer in the video.
It might seem like you have too much topping, but it's the perfect amount. It should be covered well.
This recipe is easily cut in half and baked in a 8x8 dish.